This invention relates to a protein non-adsorptive semipermeable filtration membrane and to a process for producing the same, and more particularly to a substantially protein non-adsorptive, semipermeable, filtration membrane comprising an interpenetrating polymer network which is prepared from a casting solution comprising a substantially protein non-adsorptive prepolymer polymerizable upon contact with the coagulating liquid employed in the production of the membrane, a polymer that will not react readily with the prepolymer and that is substantially insoluble in said coagulating liquid, and solvent.
Successful membrane controlled separation processes depend, in major part, upon the characteristics of the membrane utilized. Among the desired characteristics is high fouling resistance. Membranes tend to gather dissolved and suspended matter on their surfaces. The foulants include small particles, colloids, oil droplets and microorganisms. Many of these are hydrophobic, that is, in aqueous solution they recoil from water molecules and cluster together. These aggregates coat a membrane's surface and can clog its pores. For example, ultrafiltration membranes prepared from hydrophobic polymers and used to concentrate aqueous protein solutions become fouled by a buildup of a protein layer on the membrane surface. This fouling results in substantial loss of protein solute permeability relative to the permeability as measured in pure water.
Many current reverse osmosis separation systems employ a series of prefilters aided by injected coagulants and various chemicals to reduce membrane fouling. Because membranes seen to foul no matter how much the feed is pretreated, the systems also rely on regular cleansing of the membranes with oxidants, solvents and detergents. Such systems can also be backwashed under pressure. Imparting a specific electric charge to membranes has also been used to prevent fouling. In ultrafiltration and reverse-osmosis membranes, a change may serve to prevent the adsorption of particles that clog the membrane's pores. Another answer to reducing fouling which has been advocated is crossflow feed, which is the rapid passage of the feed solution under pressure past the membrane. It imparts turbulence and shear to the flow, which scours the membrane surface clean. The above-mentioned methods of preventing membrane fouling are far from perfect and can prove to be quite costly and time consuming.
Accordingly, it is a principal object of the present invention to provide an effective, efficient and relatively inexpensive method of preventing membrane fouling.
It is a further object of the present invention to provide such a method of preventing membrane fouling by providing a protein-nonadsorptive semipermeable filtration membrane which will not encounter fouling due to the protein-nonadsorptive nature of its surface.